Abstract:
The potential of combining small dimension timber with timber webs of suitable thickness has been demonstrated by of
this experimental investigation on nailed built up timber box beams of different cross sectional profiles in which the
flanges and webs are entirely of timber. No literature was available on such timber box beam construction. The effect of
web thickness, overall depth, and shape of flange on the load carrying capacity and flexural rigidity of timber box
beams were investigated. Timber beams consisting of webs of 25 mm thickness and overall depth of 225 mm were
shown to be the most cost effective. The profile of the flange does not appear to have a significant effect on either the
load carrying capacity or flexural rigidity. No attempt wa<i made to model the nail deformation on either the load
capacity or the flexural rigidity. Rather, analytical studies showed that the load capacity of the 225 mm deep built-up
all timber box beams are approximately 30% and their flexural rigidity is in the range of 25% to 40% that of an
integral hollow timber section of identical dimensions. Thus at first glance, the advantage of built up beams of these
dimensions may seem questionable. However, considering the fact that integral hollow sections of these dimensions are
not available and that there is value addition to the small dimension timber sections whose capacity in bending as solid
timber sections acting alone is very small, the all timber built up box beams have immense potential.
